U.S. patent application number 13/842672 was filed with the patent office on 2013-08-15 for composite magnetic antenna and rf tag, and metal part and metal tool on which the composite magnetic antenna or rf tag is installed.
This patent application is currently assigned to TODA KOGYO CORPORATION. The applicant listed for this patent is TODA KOGYO CORPORATION. Invention is credited to Takanori Doi, Tetsuya Kimura, Jun Koujima, Yoshiro Sato.
Application Number | 20130206847 13/842672 |
Document ID | / |
Family ID | 41318523 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130206847 |
Kind Code |
A1 |
Koujima; Jun ; et
al. |
August 15, 2013 |
COMPOSITE MAGNETIC ANTENNA AND RF TAG, AND METAL PART AND METAL
TOOL ON WHICH THE COMPOSITE MAGNETIC ANTENNA OR RF TAG IS
INSTALLED
Abstract
The present invention relates to a composite magnetic antenna
for information communication utilizing a magnetic field component
as well as a composite RF tag using the composite magnetic antenna,
which can be embedded in metals while maintaining a sufficient
communication sensitivity unlike conventional RF tags which were
unusable in the metal embedding applications. The composite RF tag
for transmitting and receiving information using an electromagnetic
induction method according to the present invention, comprises a
magnetic antenna on which an IC is mounted, and an insulating
material and a metal material or a conductive material which are
formed around the magnetic antenna, wherein the magnetic antenna
comprises a central core formed of a magnetic material, and an
electrode material formed into a coil around the central core; the
insulating material is formed around the magnetic antenna except
for one longitudinal end of the coil of the magnetic antenna; and
the metal material or the conductive material is formed on an
outside of the insulating material.
Inventors: |
Koujima; Jun;
(Hiroshima-ken, JP) ; Kimura; Tetsuya;
(Hiroshima-ken, JP) ; Doi; Takanori;
(Hiroshima-ken, JP) ; Sato; Yoshiro; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TODA KOGYO CORPORATION; |
|
|
US |
|
|
Assignee: |
TODA KOGYO CORPORATION
Otake-shi
JP
|
Family ID: |
41318523 |
Appl. No.: |
13/842672 |
Filed: |
March 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12992197 |
Jan 13, 2011 |
|
|
|
PCT/JP2009/002060 |
May 12, 2009 |
|
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13842672 |
|
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Current U.S.
Class: |
235/492 ;
336/90 |
Current CPC
Class: |
H01Q 7/08 20130101; G06K
19/07779 20130101; H01Q 1/2225 20130101; G06K 19/07771 20130101;
H01F 17/04 20130101 |
Class at
Publication: |
235/492 ;
336/90 |
International
Class: |
G06K 19/077 20060101
G06K019/077; H01F 17/04 20060101 H01F017/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 13, 2008 |
JP |
2008-126504 |
Claims
1. A composite RF tag for transmitting and receiving information
using an electromagnetic induction method, comprising a magnetic
antenna on which an IC is mounted, and an insulating material and a
metal material or a conductive material which are formed around the
magnetic antenna, the magnetic antenna comprising a central core
formed of a magnetic material, and an electrode material formed
into a coil around the central core; the insulating material being
formed around the magnetic antenna except for one longitudinal end
of the coil of the magnetic antenna; and the metal material or the
conductive material being formed on an outside of the insulating
material, wherein the RF tag is configured for transmitting and
receiving the information at 13.56 MHz.
2. A composite RF tag according to claim 1, wherein a length of the
metal material or the conductive material in a depth direction
thereof is not less than 1.0 time a longitudinal length of the
magnetic antenna.
3. A composite RF tag according to claim 1, wherein the central
core has a magnetic permeability of 70 to 120.
4. A composite RF tag for transmitting and receiving information
using an electromagnetic induction method, comprising a magnetic
antenna on which an IC is mounted, and an insulating material and a
metal material or a conductive material which are formed around the
magnetic antenna, the magnetic antenna comprising a central core
formed of a magnetic material and a non-magnetic material, and an
electrode material formed into a coil around the central core; the
insulating material being formed around the magnetic antenna except
for one longitudinal end of the coil of the magnetic antenna; and
the metal material or the conductive material being formed on an
outside of the insulating material, wherein the RF tag is
configured for transmitting and receiving the information at 13.56
MHz.
5. A composite magnetic antenna for transmitting and receiving
information using an electromagnetic induction method, comprising a
magnetic antenna, and an insulating material and a metal material
or a conductive material which are formed around the magnetic
antenna, the magnetic antenna comprising a central core formed of a
magnetic material or formed of the magnetic material and a
non-magnetic material, and an electrode material formed into a coil
around the central core; the insulating material being formed
around the magnetic antenna except for one longitudinal end of the
coil of the magnetic antenna; and the metal material or the
conductive material being formed on an outside of the insulating
material, wherein the magnetic antenna is configured for
transmitting and receiving the information at 13.56 MHz.
6. A composite magnetic antenna according to claim 5, wherein an
area ratio of all portions of the magnetic material to all portions
of the non-magnetic material is not more than 1.0.
7. A system for transmitting and receiving information using an
electromagnetic induction method, the system comprising: a metal
tool or metal part including a small-space hole; and a composite RF
tag embedded in the small-space hole, the composite RF tag
including a magnetic antenna on which an IC is mounted, and an
insulating material and a metal material or a conductive material
which are formed around the magnetic antenna, the magnetic antenna
comprising a central core formed of a magnetic material, and an
electrode material formed into a coil around the central core; the
insulating material being formed around the magnetic antenna except
for one longitudinal end of the coil of the magnetic antenna; and
the metal material or the conductive material being formed on an
outside of the insulating material, wherein the RF tag is
configured for transmitting and receiving the information at 13.56
MHz.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/992,197, filed Jan. 13, 2011, pending, which is the
U.S. national phase of International Application No.
PCT/JP2009/002060, filed May 12, 2009 which designated the U.S. and
claims priority to Japanese Patent Application No. 2008-126504,
filed May 13, 2008, the entire contents of each of which are hereby
incorporated by reference in this application.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] (NOT APPLICABLE)
BACKGROUND OF THE INVENTION
[0003] 1. Technical Field
[0004] The present invention relates to a magnetic antenna for
information communication using a magnetic field component and an
RF tag using the magnetic antenna. In the present invention, the
magnetic antenna is surrounded by a metal material or a conductive
material except for one longitudinal end of a coil thereof. As a
result, the resulting composite magnetic antenna or RF tag can be
embedded in metals while maintaining a sufficient communication
sensitivity unlike conventional RF tags which have been unusable in
such metal embedding applications.
[0005] 2. Background Art
[0006] An antenna for transmitting and receiving an electromagnetic
wave using a magnetic material (hereinafter referred to merely as a
"magnetic antenna") includes a coil formed by winding a conductive
wire around a core (magnetic material), in which a magnetic field
component coming from the outside is allowed to pass through the
magnetic material to convert the magnetic field component into a
voltage (or current) induced by the coil. Such a magnetic antenna
has been widely used in small-size radios and TVs. The magnetic
antenna is also used in a non-contact object identification device
called RF tag which has recently come into use.
[0007] To transmit and receive an electromagnetic wave with a
higher frequency, a planar loop antenna free of a magnetic material
and including a loop coil having a coil surface parallel to an
object to be identified is used in RF tags. When the frequency is
much higher (UHF band or microwave band), an electric field antenna
(dipole antenna or dielectric antenna) for detecting an electric
field component instead of a magnetic field component is widely
used in such RF tags.
[0008] However, the planar loop antenna and electric field antenna
have the following problems. That is, when such an antenna comes
close to a metal material, an image (mirror effect) is generated on
the metal material. Since the magnetic field of the image has a
phase opposite to that of the antenna, the sensitivity of the
antenna tends to be lost.
[0009] On the other hand, there is also known a magnetic antenna
for transmitting and receiving a magnetic field component which
comprises a magnetic layer as a central core, a coil-shaped
electrode material wound on the core, an insulating layer formed on
at least one outside surface of the core on which the coil-shaped
electrode material is provided, and a conductive layer formed on at
least one outside surface of the insulating layer (Patent Document
1). The magnetic antenna described in Patent Document 1 can
maintain properties required for antennas even when coming into
contact with a metal material. In addition, tags and magnetic
antennas which are installed in specific conditions are
conventionally known (Patent Documents 2 to 4).
[0010] Patent Document 1: Japanese Patent Application Laid-open
(KOKAI) No. 2007-19891
[0011] Patent Document 2: Japanese Patent Application Laid-open
(KOKAI) No. 2002-207980
[0012] Patent Document 3: Japanese Patent Application Laid-open
(KOKAI) No. 2004-362342
[0013] Patent Document 4: Japanese Patent Application Laid-open
(KOKAI) No. 2005-198255
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0014] In the method described in Patent Document 1, it is
suggested to take a certain measure in the case where the antenna
is used in the application for attachment to metals in a specific
direction. However, when embedded in metal parts or metal tools,
the antenna may fail to maintain a sufficient sensitivity.
[0015] Also, in the method described in Patent Document 2 which
aims at installation of an antenna or tag on a surface of objective
products, no consideration is taken to embed the antenna or tag in
the objective products.
[0016] Further, in the methods described in Patent Documents 3 and
4, an outer peripheral surface of the magnetic antenna is covered
and surrounded by a magnetic material. However, these methods aim
at improving a sensitivity of the magnetic antenna by covering the
magnetic antenna with a ferrite material, and may therefore fail to
solve problems concerning adverse influences by metals or
conductive materials placed therearound.
[0017] Under these circumstances, an object of the present
invention is to provide a composite RF tag or a composite magnetic
antenna which is small in size and comprises a magnetic antenna
which can maintain good properties thereof even when embedded in a
small hole formed in metals.
Means for Solving the Problem
[0018] The above object of the present invention can be achieved by
the following aspects of the present invention.
[0019] That is, in accordance with the present invention, there is
provided a composite RF tag for transmitting and receiving
information using an electromagnetic induction method, comprising a
magnetic antenna on which an IC is mounted, and an insulating
material and a metal material or a conductive material which are
formed around the magnetic antenna,
[0020] the magnetic antenna comprising a central core formed of a
magnetic material, and an electrode material formed into a coil
around the central core;
[0021] the insulating material being formed around the magnetic
antenna except for one longitudinal end of the coil of the magnetic
antenna; and
[0022] the metal material or the conductive material being formed
on an outside of the insulating material (Invention 1).
[0023] In addition, according to the present invention, there is
provided a composite RF tag for transmitting and receiving
information using an electromagnetic induction method, comprising a
magnetic antenna on which an IC is mounted, and an insulating
material and a metal material or a conductive material which are
formed around the magnetic antenna,
[0024] the magnetic antenna comprising a central core formed of a
magnetic material and a non-magnetic material, and an electrode
material formed into a coil around the central core;
[0025] the insulating material being formed around the magnetic
antenna except for one longitudinal end of the coil of the magnetic
antenna; and
[0026] the metal material or the conductive material being formed
on an outside of the insulating material (Invention 2).
[0027] Also, according to the present invention, there is provided
the composite RF tag as described in the above Invention 1, wherein
the metal material or the conductive material is formed into a
circular shape in section and has an inner diameter not less than
1.0 time a maximum length of a section of the magnetic antenna
(Invention 3).
[0028] Also, according to the present invention, there is provided
the composite RF tag as described in the above Invention 1, wherein
a length of the metal material or the conductive material in a
depth direction thereof is not less than 1.0 time a longitudinal
length of the magnetic antenna (Invention 4).
[0029] In addition, according to the present invention, there is
provided a composite magnetic antenna for transmitting and
receiving information using an electromagnetic induction method,
comprising a magnetic antenna, and an insulating material and a
metal material or a conductive material which are formed around the
magnetic antenna,
[0030] the magnetic antenna comprising a central core formed of a
magnetic material or formed of the magnetic material and a
non-magnetic material, and an electrode material formed into a coil
around the central core;
[0031] the insulating material being formed around the magnetic
antenna except for one longitudinal end of the coil of the magnetic
antenna; and
[0032] the metal material or the conductive material being formed
on an outside of the insulating material (Invention 5).
[0033] Further, according to the present invention, there is
provided a metal part comprising the composite RF tag as described
in any one of the above Inventions 1 to 4 or the composite magnetic
antenna as described in the above Invention 5 (Invention 6).
[0034] Furthermore, according to the present invention, there is
provided a metal tool comprising the composite RF tag as described
in any one of the above Inventions 1 to 4 or the composite magnetic
antenna as described in the above Invention 5 (Invention 7).
EFFECT OF THE INVENTION
[0035] The composite RF tag and the composite magnetic antenna
according to the present invention hardly undergo a change in
communication sensitivity even when embedded in a small-space hole
formed in a metal material, and, therefore, can be suitably used in
the applications such as 13.56 MHz RFID.
[0036] The composite RF tag and the composite magnetic antenna
according to the present invention have a small size and are free
from adverse influences from outside, in particular, influences by
outside metals or conductive materials, and, therefore, can be
suitably used in a state embedded in metals or the like in various
applications such as portable equipments, containers, metal parts,
boards, metal tools, various metal molds, printing plates or
printing rolls, vehicles such as bicycles and automobiles, metal
jigs, and markers such as bolts and rivets.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a conceptual view of a composite RF tag according
to the present invention.
[0038] FIG. 2 is a sectional view of a composite RF tag according
to the present invention.
[0039] FIG. 3 is a conceptual view of a magnetic antenna according
to the present invention.
[0040] FIG. 4 is a conceptual view of a magnetic antenna according
to the present invention.
[0041] FIG. 5 is a conceptual view of a magnetic antenna according
to the present invention.
[0042] FIG. 6 is a view showing a laminated structure of a coil
portion of a magnetic antenna according to the present
invention.
EXPLANATION OF REFERENCE NUMERALS
[0043] 1: through-hole; 2: electrode pattern (coil electrode); 3:
coil open end; 4: coil; 5: magnetic layer; 6: insulating layer; 7:
conductive layer; 8: non-magnetic layer; 17: magnetic antenna; 20:
insulating material; 30: metal material or conductive material; a:
maximum diameter of magnetic antenna; b: inner diameter of metal
material or conductive material; c: length in longitudinal
direction of magnetic antenna; d: length in depth direction of
metal material or conductive material
PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION
[0044] First, the composite RF tag of the present invention is
described.
[0045] In the composite RF tag according to the present invention,
an insulating material is formed around the magnetic antenna (RF
tag) on which an IC is mounted, except for one longitudinal end of
a coil (opened surface of magnetic flux) of the magnetic antenna.
In addition, a metal material or a conductive material is formed on
an outside of the insulating material. The magnetic antenna
comprises a central core formed of a magnetic material or formed of
the magnetic material and a non-magnetic material, and an electrode
material formed into a coil around the central core. The magnetic
antenna serves as an RF tag by mounting an IC thereon.
[0046] In FIGS. 1(a) to 1(d) and FIG. 2, there are shown schematic
views of the composite RF tag according to the present
invention.
[0047] As shown in the figures, the composite RF tag according to
the present invention has such a structure that a metal material or
a conductive material 30 is disposed around a magnetic antenna 17
to surround a whole peripheral surface of the magnetic antenna
except for one longitudinal end of a coil thereof, and further an
insulating material 20 is filled in a space between the magnetic
antenna and the metal material or the conductive material.
[0048] The sectional shape of the metal material or the conductive
material as used in the present invention is not particularly
limited, and may be any shape including a circular shape, an
elliptical shape, a polygonal shape such as a triangular shape, a
quadrangular shape, a pentagonal shape and a hexagonal shape, and a
star shape. In view of industrial productivity, among these shapes,
preferred is the circular shape.
[0049] In addition, the sectional shape of the metal material or
the conductive material when taken along a longitudinal direction
of the coil of the magnetic antenna may be not only a cylindrical
shape as shown in FIG. 1(a) but also a open-bottomed cylindrical
shape, a conical shape or a bottom-semispherical shape as shown in
FIGS. 1(b) to 1(d), respectively.
[0050] Meanwhile, it is not required that the metal material or the
conductive material is formed over a whole outside surface of the
insulating material. The metal material or the conductive material
may be formed so as to cover either a whole outside surface of the
insulating material or only on a gapped partial surface thereof.
Examples of the configuration of the metal material or the
conductive material on the insulating material include the
configuration where two or more curved metal materials or
conductive materials are formed on the insulating material with a
clearance therebetween so as not to come into contact with each
other, the configuration where two or more plate-shaped metal
materials or conductive materials are formed on the insulating
material with a clearance therebetween so as not to come into
contact with each other, the configuration where the metal material
or the conductive material is formed on the insulating material
with a partial clearance therebetween, the configuration where the
metal material or the conductive material having a C-shaped section
is formed on the insulating material having a circular sectional
shape, or the configuration where the metal material or the
conductive material is formed on each corner of the insulating
material having a polygonal sectional shape such as a quadrangular
sectional shape. Even when the metal material or the conductive
material is formed with a clearance therebetween, only at least one
end of the composite RF tag may be wholly covered with the metal
material or the conductive material.
[0051] In the present invention, when the metal material or the
conductive material has a circular sectional shape, the ratio of an
inner diameter of the metal material or the conductive material (c
in FIG. 2) to a maximum length of a section of the magnetic antenna
(a in FIG. 2) (c/a) is required to be not less than 1.0. The ratio
c/a is preferably not less than 1.1 and more preferably not less
than 1.3.
[0052] In addition, the ratio of a length of the metal material or
the conductive material in a depth direction thereof (d in FIG. 2)
to a length of the core in a longitudinal direction thereof (b in
FIG. 2) (d/b) is preferably not less than 1.0. When the ratio d/b
is less than 1.0, the resulting composite RF tag tends to hardly
exhibit a sufficient sensitivity. The ratio d/b is more preferably
not less than 1.2.
[0053] Also, the thickness of the metal material or the conductive
material is not particularly limited, and is preferably about 0.5
to about 2.0 mm
[0054] The metal material used in the present invention is not
particularly limited, and may be a general metal pipe material.
Examples of the metal material used in the present invention
include stainless steel, iron, aluminum, copper and brass. Examples
of the conductive material used in the present invention include a
general conductive material such as carbon, a conductive organic
material such as polyacetylene, and a composite material
thereof.
[0055] As the insulating material used in the present invention,
there may be used resins, glass ceramic materials and non-magnetic
ferrites. Examples of the suitable resins include heat resistant
resins such as polyimides, epoxy resins and phenol resins. Examples
of the suitable glass ceramic materials include borosilicate-based
glass materials and zinc-based or lead-based glass materials.
Examples of the suitable non-magnetic ferrites include Zn-based
ferrites. The resins, glass ceramics and non-magnetic ferrites may
be respectively used in the form of a mixture of any two or more
thereof.
[0056] In the RF tag according to the present invention, an IC is
mounted on the magnetic antenna. On the other hand, the RF tag may
be used as an antenna in the case where no IC is mounted on the
magnetic antenna. Further, in the composite magnetic antenna, a
wiring connected with a lead terminal of the coil of the magnetic
antenna may extend up to outside thereof and may be connected to an
IC chip disposed outside of the magnetic antenna.
[0057] Next, the magnetic antenna used in the present invention is
described.
[0058] The magnetic antenna used in the present invention is
schematically shown in FIGS. 3 to 5.
[0059] The magnetic antenna shown in FIG. 3 has a basic structure
which comprises a magnetic layer (core), an electrode material
formed into a coil shape (wire winding shape) around the central
core, and an insulating layer formed on at least one outside
surface of the core on which the coil-shaped electrode material is
formed.
[0060] In the magnetic antenna of the present invention as shown in
FIG. 3, a mixture prepared by mixing magnetic particles and a
binder is formed into a sheet shape to form a magnetic layer 5 in
the form of a single layer or a laminated layer having a plurality
of layers as shown in FIG. 6. Then, through-holes 1 are formed
through the thus formed magnetic layer 5. The electrode material is
poured into the respective through-holes 1. Also, the electrode
material is applied on both surfaces of the magnetic layer which
are perpendicular to the through-holes 1, to form an electrode
pattern 2 in the form of a coil (wire winding) which is connected
with the electrode material poured into the through-holes 1. Thus,
the coil is formed around a square or rectangular core constituted
from the magnetic layer 5. At this time, the above structure is
configured such that both terminal ends of of the magnetic layer 5
forming the coil 4 are open ends of a magnetic circuit.
[0061] Next, insulating layers 6 are respectively formed on upper
and lower surfaces of the coil 4 on which the electrode pattern is
formed.
[0062] The thus obtained sheet is cut into a desired shape along
the through-holes 1 and the open ends 3 of the coil and then
integrally sintered, or is integrally sintered and then cut into a
desired shape along the through-holes 1 and the open ends 3 of the
coil, thereby producing the magnetic antenna (LTCC technology).
[0063] The magnetic antenna shown in FIG. 4 has a basic structure
which comprises a magnetic layer (core), an electrode material
formed into a coil shape (wire winding shape) around the central
core, an insulating layer formed on at least one outside surface of
the core on which the coil-shaped electrode material is formed, and
a conductive layer formed on at least one outside surface of the
insulating layer.
[0064] In the magnetic antenna of the present invention as shown in
FIG. 4, a mixture prepared by mixing magnetic particles and a
binder is formed into a sheet shape to form a magnetic layer 5 in
the form of a single layer or a laminated layer having a plurality
of layers as shown in FIG. 6. Then, through-holes 1 are formed
through the thus formed magnetic layer 5. The electrode material is
poured into the respective through-holes 1. Also, the electrode
material is applied on both surfaces of the magnetic layer which
are perpendicular to the through-holes 1, to form an electrode
pattern 2 in the form of a coil (wire winding) which is connected
with the electrode material poured into the through-holes 1. Thus,
the coil is formed around a square or rectangular core constituted
from the magnetic layer 5. At this time, the above structure is
configured such that both terminal ends of of the magnetic layer 5
forming the coil 4 are open ends of a magnetic circuit.
[0065] Next, insulating layers 6 are respectively formed on upper
and lower surfaces of the coil 4 on which the electrode pattern is
formed.
[0066] In addition, a conductive layer 7 is formed on an upper
surface (outside surface) of at least one of the insulating layers
6.
[0067] The thus obtained sheet is cut into a desired shape along
the through-holes 1 and the open ends 3 of the coil and then
integrally sintered, or is integrally sintered and then cut into a
desired shape along the through-holes 1 and the open ends 3 of the
coil, thereby producing the magnetic antenna (LTCC technology).
[0068] The magnetic antenna shown in FIG. 5 according to the
present invention has a basic structure which comprises a central
core formed of a magnetic material 5 and a non-magnetic material 8,
an electrode material formed into a coil shape (wire winding shape)
outside of the central core, an insulating layer formed on at least
one outside surface of the central core on which the coil-shaped
electrode material is formed. The core has such a structure in
which the magnetic material is divided into plural parts by the
non-magnetic material.
[0069] Meanwhile, in the magnetic antenna as shown in FIG. 5, when
viewed in section of the core, the area ratio of all portions of
the magnetic material to all portions of the non-magnetic material
(all portions of the magnetic material/all portions of the
non-magnetic material) is preferably not more than 1.0. When the
area ratio of the portions formed of the non-magnetic material
exceeds the above-specified range, the proportion of the magnetic
material in the core is reduced, which tends to be disadvantageous
for achieving reduction in size of the magnetic antenna. The area
ratio of all portions of the magnetic material to all portions of
the non-magnetic material in the core is more preferably not more
than 0.5, and still more preferably not more than 0.2.
[0070] Meanwhile, in the magnetic antenna as shown in FIG. 5, the
ratio of a sectional area (S) of one of the magnetic layers forming
the core of the magnetic antenna as shown in FIG. 5 to a length (L)
of the magnetic antenna (S/L) is preferably not more than 0.3. When
the area ratio (S/L) is more than 0.3, it may be difficult to
reduce adverse influences owing to a demagnetizing field.
[0071] In the present invention, the magnetic antenna having such a
core as shown in FIG. 5 may be produced, for example, by the
following method.
[0072] First, a mixture prepared by mixing magnetic particles and a
binder is formed into a sheet shape to form a magnetic layer in the
form of a single layer or a laminated layer having a plurality of
layers.
[0073] Separately, a mixture prepared by mixing non-magnetic
particles and a binder is formed into a sheet shape to form a
non-magnetic layer in the form of a single layer or a laminated
layer having a plurality of layers.
[0074] Next, as shown in FIG. 6, the magnetic layers 5 and the
non-magnetic layers 8 are alternately laminated to obtain a
laminate having a desired total thickness.
[0075] Then, a desired number of through-holes 1 are formed through
the thus obtained laminate comprising the magnetic layers and the
non-magnetic layers. The electrode material is poured into the
respective through-holes. Also, the electrode material is applied
on both surfaces of the laminate which are perpendicular to the
through-holes, to form an electrode pattern 2 in the form of a coil
(wire winding) which is connected with the electrode material
poured into the through-holes. The electrode material poured into
the through-holes and the electrode pattern cooperate with each
other to form a coil having a square or rectangular core
constituted from the magnetic layers. At this time, the above
structure is configured such that both terminal ends of of the
magnetic layers constituting the coil are open ends of a magnetic
circuit (refer to numeral 3 in FIG. 4).
[0076] Next, insulating layers 6 are respectively formed on upper
and lower surfaces of the coil on which the electrode pattern is
formed, as shown in FIG. 5.
[0077] The thus obtained sheet is cut into a desired shape along
the through-holes and the open ends of the coil and then integrally
sintered, or is integrally sintered and then cut into a desired
shape along the through-holes and the open ends of the coil,
thereby producing the magnetic antenna (LTCC technology).
[0078] In the magnetic antenna of the present invention, as the
magnetic material of the core, there may be used Ni--Zn-based
ferrite, etc. The Ni--Zn-based ferrite used in the present
invention preferably has a composition comprising 45 to 49.5 mol %
of Fe.sub.20.sub.3, 9.0 to 45.0 mol % of NiO, 0.5 to 35.0 mol % of
ZnO and 4.5 to 15.0 mol % of CuO. The ferrite composition may be
suitably selected such that the resulting core as the magnetic
material thereof has a high magnetic permeability and a low
magnetic loss in a frequency band to be used. When using a material
having an excessively high magnetic permeability as the magnetic
material, the resulting core tends to undergo an increased magnetic
loss and as a result, tends to be unsuitable for antennas.
[0079] For example, the ferrite composition is preferably selected
such that the core has a magnetic permeability of 70 to 120 at
13.56 MHz when the magnetic antenna is applied to an RFID tag, and
has a magnetic permeability of 10 to 30 at 100 MHz when the
magnetic antenna is used to receive commercial FM broadcasts,
because the magnetic loss can be reduced.
[0080] Also, in the magnetic antenna of the present invention, a
coil lead terminal and an IC chip connecting terminal both formed
of the electrode material may be formed on an outside surface of
the insulating layer to connect an IC therewith.
[0081] The magnetic antenna provided therein with the above IC chip
connecting terminal may be produced as follows. That is,
though-holes 1 are formed through the insulating layer 6 disposed
on at least one surface of the coil 4 on which the electrode
pattern is formed. The electrode material is poured into the
through-holes 1, and connected with both ends of the coil 4. Thus,
the coil lead terminal and the IC chip connecting terminal both
formed of the electrode material is formed on the surface of the
insulating layer, and the thus produced structure is then
integrally sintered to produce the magnetic antenna.
[0082] In addition, in the magnetic antenna of the present
invention, a capacitor electrode may be disposed on the outside
surface of the insulating layer. Further, an additional insulating
layer may be provided on the outside surface on which the capacitor
electrode is disposed.
[0083] Also, the magnetic antenna of the present invention may have
a parallel electrode or an interdigital electrode printed on the
outside surface of the insulating layer to form a capacitor. In
addition, the capacitor may be connected in parallel or in series
to the coil lead terminal.
[0084] Further, in the magnetic antenna of the present invention,
the insulating layer may be further provided on the outside surface
where the capacitor electrode is disposed, with an additional
insulting layer. In addition, an electrode which also serves as an
IC chip connecting terminal may be further formed on an outside
surface of the additional insulating layer such that the insulating
layer is sandwiched therebetween, to form a capacitor which may be
connected in parallel or in series to the IC chip terminal.
[0085] In addition, in the magnetic antenna of the present
invention, the insulating layer may be provided on the outside
surface with a terminal structure to which an IC chip can be
connected, so as to connect the IC chip connecting terminal and the
coil lead terminal in parallel or in series to each other.
[0086] Also, in the magnetic antenna of the present invention, the
insulating layer may be provided on the outside surface with a
terminal for providing a variable capacitor, so as to connect the
coil lead terminals in parallel or in series to each other.
[0087] In the magnetic antenna of the present invention, as the
magnetic material of the core, there may be used Ni--Zn-based
ferrite, etc. The Ni--Zn-based ferrite used in the present
invention preferably has a composition comprising 45 to 49.5 mol %
of Fe.sub.2O.sub.3, 9.0 to 45.0 mol % of NiO, 0.5 to 35.0 mol % of
ZnO and 4.5 to 15.0 mol % of CuO. The ferrite composition may be
suitably selected such that the resulting core as the magnetic
material thereof has a high magnetic permeability and a low
magnetic loss in a frequency band to be used. When using a material
having an excessively high magnetic permeability as the magnetic
material, the resulting core tends to undergo an increased magnetic
loss and as a result, tends to be unsuitable for antennas.
[0088] For example, the ferrite composition is preferably selected
such that the core has a magnetic permeability of 70 to 120 at
13.56 MHz when the magnetic antenna is applied to an RFID tag, and
has a magnetic permeability of 10 to 30 at 100 MHz when the
magnetic antenna is used to receive commercial FM broadcasts,
because the magnetic loss can be reduced.
[0089] In the magnetic antenna of the present invention, as the
non-magnetic material of the core, there may be used non-magnetic
ferrites such as Zn-based ferrites, glass-based ceramic materials
such as borosilicate glass, zinc-based glass and lead-based glass,
or mixtures obtained by mixing the non-magnetic ferrite and the
glass-based ceramic material at an adequate mixing ratio.
[0090] The ferrite powder used as the non-magnetic ferrite may be
selected so as to have such a Zn-based ferrite composition that a
sintered body of the ferrite powder has a volume resistivity of not
less than 10.sup.8 .OMEGA.cm. The Zn-based ferrite composition
preferably comprises 45 to 49.5 mol % of Fe.sub.2O.sub.3, 17.0 to
22.0 mol % of ZnO and 4.5 to 15.0 mol % of CuO.
[0091] The glass-based ceramic powder used as the glass-based
ceramic material may be selected so as to have such a composition
that its linear expansion coefficient is not largely different from
that of the magnetic material used. More specifically, the
composition is preferably selected such that the difference in
linear expansion coefficient between the glass-based ceramic powder
and a soft magnetic ferrite used as the magnetic material lies
within the range of .+-.5 ppm/.degree. C.
[0092] Next, the process for producing the composite RF tag
according to the present invention is described.
[0093] The composite RF tag of the present invention may be
produced by disposing a conductive material or a metal material
around the above IC-mounted magnetic antenna obtained by the above
method so as to surround an outer peripheral portion of the
magnetic antenna except for one longitudinal end thereof, and
filling a resin into a gap between the magnetic antenna and the
conductive material or the metal material. Alternatively, the
magnetic antenna may be dipped in the resin to coat the magnetic
antenna therewith, followed by drying the resulting resin coat, and
then a metal or conductive paste may be applied on the surface of
the thus dried resin coat.
[0094] The composite RF tag of the present invention may be
embedded in a recessed portion with a desired shape which is formed
in metal parts, metal tools, etc. In this case, the objectives such
as metal parts and metal tools to which the antenna or tag is to be
installed, may be previously formed with the recessed portion with
a desired shape.
[0095] Meanwhile, the composite RF tag of the present invention is
preferably installed to the metal pars or metal tools such that the
longitudinal direction of the coil thereof (opened surface of
magnetic flux) is perpendicular to a reader therefore.
[0096] <Function>
[0097] The magnetic antenna of the present invention is formed such
that an outer peripheral portion thereof is surrounded by the metal
material or the conductive material. Therefore, when the magnetic
antenna is embedded in metal objectives, it is possible to minimize
adverse influences on a communication sensitivity thereof owing to
change in environmental conditions without variation of properties
such as resonance frequency.
EXAMPLES
[0098] In the followings, the present invention is described in
more detail on the basis of preferred embodiments thereof by
referring to the accompanying drawings.
RF Tag 1
[0099] In order to form a magnetic layer, 100 parts by weight of
calcined Ni--Zn--Cu ferrite particles which had been found to be a
material having a magnetic permeability of 100 as measured at 13.56
MHz after sintering at 900.degree. C. (Fe.sub.2O.sub.3: 48.5 mol %;
NiO: 25 mol %; ZnO: 16 mol %; CuO: 10.5 mol %), 8 parts by weight
of a butyral resin, 5 parts by weight of a plasticizer, and 80
parts by weight of a solvent were mixed in a ball mill to prepare a
slurry. The resulting slurry was applied on a PET film with a size
of 150 mm.times.150 mm by a doctor blade such that the thickness of
the coating layer obtained upon sintering was 0.1 mm, thereby
obtaining a sheet.
[0100] In order to form a non-magnetic layer, 100 parts by weight
of a borosilicate glass (SiO.sub.2: 86 to 89% by weight;
B.sub.2O.sub.3: 7 to 10% by weight; K.sub.2O: 0.5 to 7% by weight),
8 parts by weight of a butyral resin, 5 parts by weight of a
plasticizer, and 80 parts by weight of a solvent were mixed in a
ball mill to prepare a slurry. The resulting slurry was applied on
a PET film with a size of 150 mm.times.150 mm by a doctor blade
such that the thickness of the coating layer obtained upon
sintering was 0.05 mm, thereby obtaining a sheet.
[0101] Also, an insulating layer was formed in the same manner as
defined above. That is, 100 parts by weight of calcined Zn--Cu
ferrite particles (Fe.sub.2O.sub.3: 48.5 mol %; ZnO: 41 mol %; CuO:
10.5 mol %), 8 parts by weight of a butyral resin, 5 parts by
weight of a plasticizer, and 80 parts by weight of a solvent were
mixed in a ball mill to prepare a slurry. The resulting slurry was
applied on a PET film with the same size and thickness as those for
the magnetic layer using a doctor blade, thereby obtaining a
sheet.
[0102] Next, as shown in FIG. 6, through-holes 1 were formed
through the green sheet for the magnetic layer, and filled with an
Ag paste. In addition, an Ag paste was printed on both surfaces of
the sheet which were perpendicular to the through-holes 1. The ten
sheets thus prepared above were laminated on one another to form a
coil.
[0103] Next, as shown in FIG. 5, the green sheets for the
insulating layer were laminated on upper and lower surfaces of the
coil 4.
[0104] The thus laminated green sheets were bonded together while
applying a pressure thereto. The resulting laminate was cut along
the through-holes and the coil open ends 3, and integrally sintered
at 900.degree. C. for 2 hr, thereby obtaining a magnetic antenna 1
with a size of 10 mm in width.times.3 mm in length having a coil
winding number of 23 turns (in the figures, the coil is shown as
having a smaller number of turns for the sake of simplicity, and
the magnetic layers laminated are also shown as being formed of
only three layers for the sake of simplicity, which also applies to
the following other figures).
[0105] Further, an IC for an RF tag was connected to both ends of
the coil of the magnetic antenna, and a capacitor was connected in
parallel to the IC. Then, the resonance frequency was adjusted to
13.56 MHz under the condition that the resulting magnetic antenna
was surrounded by a metal material or a conductive material,
thereby obtaining an RF tag.
[0106] The thus obtained RF tag was enclosed in a metal (stainless
steel) tube having an outer diameter of 6 mm, an inner diameter of
5 mm and a length of 15 mm such that one end of the magnetic
antenna was aligned with a periphery of the metal tube and centers
of the magnetic antenna and the metal tube were positioned
concentrically to each other. Then, an epoxy resin was filled in a
clearance formed between the RF tag and the metal tube, and the
other open end of the metal tube was closed with a lid formed of a
metal (stainless steel) plate to produce a composite RF tag.
[0107] At this time, the ratio of the inner diameter of the metal
tube (c in FIG. 2) to the maximum length of a section of the
magnetic antenna (a in FIG. 2) (c/a) was 1.4, and the ratio of the
length in a depth direction of the metal tube (d in FIG. 2) to the
length in a longitudinal direction of the magnetic antenna (b in
FIG. 2) (d/b) was 1.5.
[0108] The thus obtained composite RF tag was installed into a
recess having an inner diameter of 6 mm and a depth of 15 mm which
was opened in an SUS block having a height of 5 cm and a section of
5 cm square to conduct the following measurements before and after
the installation.
[0109] [Methods for Measuring and Adjusting Resonance
Frequency]
[0110] The resonance frequency was determined from a peak frequency
of an impedance as measured using an impedance analyzer "4291A"
manufactured by Agilent Technology Co., Ltd.
[0111] [Method for Measuring Communication Distance]
[0112] The communication distance was measured by the following
method. That is, a tip end of an antenna of a pen-type
reader/writer (product name "TR3-PA001/TR3-M001B" manufactured by
Takaya Co., Ltd.) which underwent a relatively less influence from
external metal materials, was oriented to one end of the thus
prepared RF tag which was uncovered with the metal material or the
conductive material, and the RF tag was placed at the position as
remote from the antenna as possible within the range in which
communication therebetween was still possible at 13.56 MHz, and the
distance between the antenna and the RF tag was determined as the
communication distance.
RF tag 2: Comparative Example
[0113] An IC was mounted on the magnetic antenna produced in the
same manner as defined in Example 1. The resonance frequency of the
IC-mounted magnetic antenna was adjusted as such to 13.56 MHz,
thereby producing an RF tag. The thus obtained RF tag was coated
with an epoxy resin such that the obtained composite RF tag was
able to be installed in the above SUS block in the same manner as
defined above to evaluate properties thereof
TABLE-US-00001 TABLE 1 Communication distance Before Resonance
frequency embedded After Before After Example and in metal embedded
in embedded in embedded in Comparative block metal block metal
block metal block Example (mm) (mm) (MHz) (MHz) Antenna 1 7.0 7.0
13.6 13.6 Antenna 2 10.0 communication 13.6 16.2 (Comparative not
Example) possible
[0114] As shown in Table 1, when the composite RF tag uncovered
with the metal material was embedded in the metal material, the
communication with the reader was not possible.
[0115] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention is not to be
limited to the disclosed embodiments, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *